Tweaking the Mark XII: Part 2.3 – Part 1

OnSeptember 16, 2002

TWEAKING THE MARK XII: PART 2.3

ADJUSTING THE MARK XII/887

by Walt Odets

In Part 1 of this series, I revealed the installation of an IWC caliber 887 in the Mark XII and promised to spend some time adjusting the movement to see if it’s performance could be improved upon. In Part 2.1, I discussed the concepts of adjustment and timing, and in Part 2.2, the specific principles used in adjustment. In this final part of the series, I will chronicle my extensive efforts to improve the performance of the beautiful caliber 887.

These efforts will be presented in great detail, and for many readers merely scanning the results will suffice. For those who wish to see how adjustment principles actually play out in practice, much of the detail may be of interest. But this final chronicle should make one thing clear to all: the adjustment of a watch by hand is a complex, time-consuming, and sometimes unsure enterprise, particularly with flat, refined, and complex movements like the 887. While, today, the factory (and “factory service”) installs computer-timed “balances-complete” (balance, staff, spring, and rollers as a single assembly), hand adjustment is what it has always been–painstaking, slow, extremely delicate work. And, today, it must be executed on much smaller calibers than those familiar to watchmakers of only 30 years ago. My work on the caliber 887 escapement was conducted almost exclusively at seven to 35 power magnification, with a Nikon SMZ-1B industrial, stereo microscope.

ABOUT THE FIVE POSITIONS

Traditional five-position adjusting specifies positions in the following order, from most to least important: dial-up, dial-down, crown-down, crown-left, and crown-up. Although dial-down is an important position in terms of diagnostics (of faults in the watch), it is relatively unimportant in the daily use of a watch. Thus, I will often refer to to “the two important positions” as dial-up and crown-down, which constitute the majority of a watch’s positioning in actual use. Dial-up is the usual position for a watch left at night. (If a metal bracelet does not allow a dial-up position at night, an adjusted watch should usually be left crown-down.) Crown-down is experienced arm hanging, while standing or walking. For an owner wearing the watch on the outside of either wrist, crown-left is third most important position, that held with the arm on the arm of a chair or resting on a desk. Thus in adding this third position, we include virtually the entire use of a wristwatch for the left-wrist wearer. Traditional five position adjusting adds crown up, which is most significant for the right-wrist wearer, and should be substituted for crown down as the third most important position for such use. For the owner wearing the watch on the inside of the right wrist, crown right is normally adjusted, crown-left deleted. Finally, barring defects in the watch, dial-down should fall very close to dial-up.

It should be noted that during adjustment of a watch, the absolute rate of the watch is of little interest–it is the spread between positions that is of concern. Absolute rate can be easily adjusted with the regulator when adjustments are complete, and good absolute rate usually requires correction for the owner’s personal error. Most individuals introduce a losing personal error; a minority introduce a gaining personal error.

THE WAY IT WAS

The caliber 887, as delivered from the factory in an IWC Ingenieur, showed excellent adjustment. Measured on an Elma Watch-Matic in April of 1998, it showed five seconds variation between the slowest and fastest positions, and an exceptionally clean trace. Amplitude was strong dial up, and showed remarkably little drop in the vertical positions, particularly the important crown down position. While we expect about a 45 degree drop from horizontal to vertical positions, the 887 showed a mere 10 degrees from dial-up to crown-down, suggesting extremely low balance pivot friction. Had the horizontal amplitude been on the low side with such little spread to the vertical, I might have suspected a problem with the pivots tips. Pivot tip damage (or damage to the cap jewel that the tip rides on) can reduce horizontal amplitude with little effect on amplitude in vertical positions. Thus close amplitude between horizontal and vertical positions, combined with low amplitude in these positions, suggests pivot tip (or cap jewel) problems, including inadequate lubricant on the cap jewel.

The following table, like all that follow, indicates positions as seen from the dial side. Amplitude is expressed in degrees of arc; rate is in seconds error per day (relative to the quartz reference in the timer); beat is shown as error in milliseconds (e.g. “0.1″ is one-tenth of one millisecond).

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

292

288

282

263

273

275

RATE

+7

+5

+5

+10

+7

+6

BEAT ERROR

0.2

0

0

0.1

0.1

0.2

These excellent figures would be difficult to improve upon.

1.

I completely disassembled the watch, cleaned it, and lubricated it to factory specifications. The only deviation from factory lubrication entailed the substitution of Moebius 9020 (synthetic) for Moebius 8141 (a non-synthetic). The mainspring barrel was lubricated with Glissalube 20 on the barrel walls and Moebius 8201 on the mainspring itself, and on the barrel floor and top. No intentional adjustments were made to the escapement, although removal of a balance cock from a movement necessarily puts some forces on the balance spring and regulator. Following the service, regulation with the Triovis adjuster and movable stud carrier was carried out. As show at left, gross adjustments of rate are made by moving the regulator itself (red arrows). Very fine rate adjustments are made by turning the Triovis screw (at the orange arrow), which moves the regulator in very fine increments. Beat is adjusted by moving the stud carrier (blue arrows), which shifts the outer attachment of the spring. Following service, regulation of rate and beat produced the following figures.

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

320

312

290

294

286

291

RATE

-3

+3

+6

+3

+6

+6

BEAT ERROR

0.1

0.1

0

0.2

0.1

0.1

It is noteworthy that these significantly different figures are a result of nothing more than disassembly, cleaning, lubrication, and reassembly. Although relative amplitude (between horizontal and vertical) remains approximately in original proportions, overall amplitude is higher, probably due to changes in the barrel lubrication which allowed more tension at full wind (less slip of the bridle). Cleaning and lubrication of the gear train also generally improve amplitude because of decreased friction and improved power transfer to the escapement. The spread between dial-up and crown-down amplitude, 30 degrees, is now three times the original figure (more typical, probably due to improved lubrication of the pivot tips). Overall adjustment, however, is not as good as the original figures. There is now a nine second spread from fastest to slowest positions and this spread is, unfortunately, between the “260″ height=”238″ align=”RIGHT” border=”2″ naturalsizeflag=”3″ alt=”Engraving on barrle bridge”>two most critical positions, dial up and crown down. There is also a six second difference between dial up and dial down positions.

2.

The dial up/down discrepancy required correction before any other adjustments could be carried out. Because there was little difference in amplitude between the two positions (eight degrees), I suspected the rate difference was more likely due to non-parallelism of the regulator index than a fault in the balance pivots or their lubrication. I thus made a very slight adjustment to the regulator index (opening it at the bottom), demagnetized the movement, and reregulated the watch for rate and beat. This produced similar figures, but the dial up/down discrepancy was, in fact, worsened.

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

318

302

RATE

-5

+4

BEAT ERROR

0.1

0

3.

At this point, there was enough amplitude difference between the two positions, that the lower dial-down amplitude might be playing at least some role in the faster rate. But a 16 degree amplitude difference is probably not enough, by itself, for a 9 second difference. Were amplitude the issue, the balance pivots, pivot lubrication, and KIF shock absorbers would have to be checked for irregularities and differences between the two pivots. Dial up, the balance is supported largely on the upper pivot tip, dial down on the lower.

The faster dial down rate (without a larger amplitude difference) suggested that the balance index was still tighter at the bottom than at the the top. Although misalignment was not visible at 35 power magnification, I very slightly opened the regulator space at the bottom still further (blue arrow), and also shifted the stud in the stud carrier up slightly (red arrows). Although a shift would cause the spring to be a bit out of flat, the shift was so slight (.1 mm or so) that any tilt introduced was imperceptible. The change in stud height did allow the spring to ride a touch higher in the regulator (green arrow). The results, however, were not promising:

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

320

301

RATE

-2

+6

BEAT ERROR

0.1

0

The amplitude difference persisted and seemed increasingly the cause of the dial-up/dial-down rate difference. I decided to let the watch run overnight and “settle in,” rewound it fully in the morning and found the following results on the timer.

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

311

298

276

284

267

271

RATE

+5

+13

+16

+12

+20

+20

BEAT ERROR

0

0.1

0.2

0.1

0

0.2

The over-all slight decrease in amplitude (and, thus, increase in rate) was expected, for a slight deterioration in amplitude is typical of freshly service watches as lubricants distribute themselves. The dial-up/dial-down spread of eight seconds remained, but now there was a substantial spread of 15 seconds between dial-up and crown-up (it had earlier been in the 2-9 second range). At this point it was clearly time for some more work on the escapement.

4.

I lowered the stud in the stud carrier to its original position, as this had solved nothing (and put the spring slightly, if imperceptibly, out of flat). I then cleaned and reoiled the shock-jewel assembly on the upper pivot. I might have redone the lower pivot, because dial down the balance rides on the lower pivot, and the amplitude was lowest dial down. But, the original oil drop on the upper pivot was a bit on the small side (about one-third the diameter of the cap jewel instead of the one-half preferred), and the size of the drop has some relation to the endurance of the lubrication. I felt that this smaller oil drop might have reduced the drag enough to produce the amplitude difference I observed. In other words, I was trying to equalize the drag on the upper and lower pivots by increasing the drag on the upper pivot, which is not normally the desirable approach. The reoiled upper pivot is shown above left, the yellow arrow indicating the edge of the circular oil drop. Following this work I reregulated rate and beat, yielding the following figures:

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

301

293

261

273

266

266

RATE

-3

+2

+11

+6

+11

+13

BEAT ERROR

0.1

0

0

0.2

0.1

0.1

5.

The amplitude difference between dial-up and dial-down was, indeed, reduced a bit (from 19 to 8 degrees); and the rates were closer, within 5 seconds. The critical dial-up/crown-down difference, however, had increased from 11 seconds to 14 seconds. Crown-left and crown-up maintained approximately the same spread from dial-up. At this point, horizontal centering of the spring seemed the likely cause for the remaining differences, and I made extremely small adjustments to both the regulator sweep and dog leg, both with the balance installed in the watch. (This can be difficult because the balance cock obscures some of the spring.) I then reregulated for rate and beat, yielding the following figures:

DIAL UP

DIAL DOWN

CROWN DOWN

CROWN LEFT

CROWN UP

(CROWN RIGHT)

AMPLITUDE

301

281

266

271

266

263

RATE

-19

-4

-3

-7

+1

-3

BEAT ERROR

0.1

0

0

0.2

0.1

0.1

6.

The situation between dial-up and dial-down had been worsened again, but it was now largely the dial-up position that was out of line with the other figures. All other figures are within 8 seconds and the improved horizontal centering had brought the vertical positions into better adjustment. (A large change in rate with little change in amplitude implicates centering.) The dial-down amplitude suddenly seemed inexplicably on the low side, but I decided to ignore it for the time being. The very slow dial-up rate suggested that, in adjusting the regulator sweep, I had inadvertently opened up the index at the top. As adjustment of the sweep involves reshaping and bending the spring, the delicate brass index (with a diameter of about 0.10 millimeters) is easily distorted. I tightened the index high, and spread it very slightly low (blue arrows, above right). Without any reregulation, the figures were: